(CNN) -- Approximately 80,000 chickens exposed to feed tainted with the industrial chemical melamine have been declared safe for human consumption, federal health officials said Friday.

After inspections and tests of the animals on several Indiana farms, the Food and Drug Administration and the U.S. Department of Agriculture said the poultry could be released and has been approved for processing.

The birds were withheld from the food supply after it was discovered that their feed had included pet food scraps tainted with melamine, which had contaminated food additives purchased from China.

Also Friday, Chenango Valley Pet Foods added eight more pet foods, including the first ferret food, to the nationwide recall. The company said the ferret food was added to the pet food recall after the manufacturer disclosed risk of cross-contamination with other pet foods previously found to be adulterated.

The seven other products recalled by Chenango were various dog and cat foods.

And on Thursday, Dr. David Acheson, the FDA's assistant commissioner for food protection, told reporters that fish at two U.S. commercial hatcheries were also safe for consumption after testing negative for melamine, despite exposure to melamine-tainted feed imported from Canada.

Calls to the two hatcheries -- Kona Blue in Kailua-Kona, Hawaii and Seattle-based American Gold Seafoods -- were not returned Friday by the time this report was filed.

Acheson also said fish from 196 non-commercial fish farms at undisclosed locations were of "no risk to humans."

On Tuesday, the FDA announced that 56,000 swine fed pet-food scraps containing melamine had been released for slaughter and eventual human consumption.

Tests on the swine, fish and poultry found that melamine does not accumulate in the animals and the risk to humans consuming the meat is very low, the FDA said.

Probe expanded to China

A team of FDA investigators returned from China last week, after investigating where the tainted material originated. Officials said the team is concentrating on more than the two companies believed to have exported the melamine in wheat flour mislabeled as wheat gluten and rice protein concentrate.

An import alert for all 46 shipments of vegetable protein from China to the United States remained in place, and those products have yet to be proven melamine-free, Acheson said.

As part of the FDA's domestic protein surveillance assignment, 63 samples of protein from Arizona, California, Connecticut, New Hampshire, Iowa and Minnesota have not tested positive for melamine yet, but 23 of those test results are pending.

The pet food investigation was launched after Toronto, Canada-based Menu Foods recalled over 60 million cans of wet cat and dog food on March 16. The recall has since expanded to include hundreds of brands of pet food.

Thousands of pet owners have claimed their pets died after consuming the tainted products.

Earlier this week, Menu Foods posted claims forms on its Web site for U.S. and Canadian pet owners related to the recall after receiving "hundreds of thousands of calls" from customers.

While dozens of lawsuits have been filed against Menu Foods by pet owners, the company said it will begin discussions with customers who wish to settle with Menu Foods directly, out of court.

On May 31, a panel of judges from multiple districts nationwide will be holding a hearing in Las Vegas, Nevada, to decide if 70-plus lawsuits against pet food manufacturers, both those seeking class action status and otherwise, should be heard by one court.

The lawyers for suits in several of those states have filed a petition for all the cases nationwide to be heard in a court in their district, according to Catherine Odenbreit, a lawyer representing multiple plaintiffs in several state and federal suits filed in California.